I tried to program the bootloader by using two miniwireless boards - one functioning as ArduinoISP (a process I've done many times with many type of Arduinos) and it failed.
One board is driven by a CP2101 connected to the PC USB. I run the 5V from the CP2101 to both boards, program the connected one with ArduinoISP sketch, and then run wires between the boards:
11->11
12->12
13->13
10->RST
Not working. I get this error message:
avrdude: Yikes! Invalid device signature.
Double check connections and try again, or use -F to override
this check.

What gives?
PS. tried to program a miniwireless with an Uno at first. Got the same message. Suspected 3.3V/5V compatibility issues. Wrong direction.

If you are trying to bootload with the radio installed, the problem you are having is most likely caused by D10 on the RFM radio floating and appearing as a LOW. Thus asserting the SPI radio interface when you're trying to program the CPU. As a result an error is thrown as you have experienced. The solution is to pull-up the D10 input while doing the bootload.
This just happened to me today, as I was needing to bootload some devices that had RFM69xx radios installed. As soon as I pulled D10, it worked fine.
I just submitted a new design in the low power series, and I've added a 100K resister to D10 for this very reason.
Please try this, and let me know if you have further issues in this regard.

It appears that my MiniWireless boards did not ship with a bootloader installed (or at least I couldn't get them to work). I reflashed the bootloader using the Duelimanove w/ ATmega328 option using a Pro Mini as the ISP. This required the the 100k fix mentioned below. No other modifications required (such as the recommended 10uF cap on reset on the UNO from the Arduino site). It did not work without it.

Thanks for your Post.
I don't see how this would be possible, because in our internal process, ALL miniwireless boards without exception, are both bootloaded and programmed with a test routine prior to shipping. The boards then MUST pass QA test which includes RTC coding with sleep/interrupt processing, and Memory read/write tests before they are allowed move over to be packaged or joined with a radio. After reading your post, I called our Technician responsible for this, and he concurred as well, that there is strict adherence to testing procedure. The importance of this was further reinforced in my communication with him just now.
We work hard to do our best for customers in both quality and service, and we are always open to learn and improve. Any comments, criticisms, complements, and such, are welcomed.

I'm stumped.
I managed to program some of my MiniWireless (about half of the 8 I have). Half of them will not program. I suspect two of them have dead AVRs for some reason (ordered new AVRs and will replace). One has a working AVR - it runs my code just fine. However, I cannot burn a bootloader. Got an AVR DRAGON (which has level shifters) and it wouldn't detect the AVR. Pulled D10 up. Even pulled D5 up just in case. Looking at the ISP siganls with a logic analyzer I can see SCK and MOSI toggling but MISO stays high. RST goes high to low before transaction and back up afterwards.
What am I missing here? I must have a watchdog-enabled bootloader for my projects - the RFM69 libraries have some RAM leakage that I didn't manage to trace and a watchdog is essential...
Thanks.